National Electric MFGTemporary power • HVAC load tools
Methodology

Electrical calculator · RCD Type A / Type AC / compressor / inverter

RCD Type Selector for HVAC Loads

A selector aid for AC, dehumidifiers, inverter drives, electronic controls and mixed temporary HVAC equipment.

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For discussing protection type with a qualified electrician or designer.

Field notes

Field notes for RCD type selector

Practical checks to run before this calculator result turns into a site decision.

Site check

Start with the weakest part of the temporary supply

The limiting point is often not the headline supply size. Check plug rating, extension length, reel state, transformer rating, RCD/RCBO sharing and the smallest protective device in the chain.

Site check

Allow for rough starts and wet-site behaviour

Compressors, pumps and long leads can behave badly at start-up. Treat amber results as a prompt to split circuits, stagger starts or move the load closer to the board.

Site check

Keep a short job-file note

Record the entered load, assumed voltage, cable run and any decision to split equipment. It makes later fault finding and handover conversations much cleaner.

FAQ

RCD type selector FAQ

Short answers for UK temporary electrical and HVAC planning.

What is the RCD type selector used for?

A selector aid for AC, dehumidifiers, inverter drives, electronic controls and mixed temporary HVAC equipment. It is mainly for temporary HVAC, drying, cooling and site-power planning, especially where a quick pre-check is needed before selecting equipment or changing a temporary setup.

Can this replace BS 7671 design, inspection or testing?

No. Treat it as a pre-check for the conversation or job file. Final decisions still need current BS 7671 requirements, manufacturer data, inspection, testing, risk assessment and the actual site conditions.

What should I verify before acting on the result?

Check supply rating, protective device rating, cable length, voltage drop, start current, phase balance and the condition of temporary leads or distribution boards. If any assumption is uncertain, use the result as a prompt to investigate rather than as clearance to switch on.

What does an amber or red result usually mean?

It normally means the margin is weak, an assumption is missing, or the load should be split, staged, moved closer to the supply, reduced or checked by a qualified electrician before use.

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